As elevator systems have become more sophisticated, for instance having a large number of elevators operating as a group to service a large number of floors, a need developed for determining the manner in which calls for service in either the up or down direction registered at any of the floor landings of the building are to be answered by the respective elevator cars. The most common form of elevator system group control divides the floors of the building into zones, there being one or several floors in each zone, with approximately the same number of zones as there are cars in the elevator system which can respond to group-controlled service of floor landing calls. However, this approach has had a number of drawbacks.
A more recent innovation, described in the commonly owned U.S. Pat. No. 4,363,381 of Joseph Bittar issued Dec. 14, 1982, included the provision of an elevator control system in which hall calls are assigned to cars based upon relative system response (RSR) factors, which take into account instantaneous system operating characteristics in accordance with a desirable scheme of operation. This scheme includes considering a plurality of desirable factors, the assignments being made based upon a relative balance among the factors in making the ultimate selection of a car to answer a hall call. The previous Bittar invention thus provided a capability of assigning calls on a relative basis, rather than on an absolute basis, and, in doing so, used specific, pre-set values for assigning the RSR "bonuses" and "penalties".
As conditions changed, the factors changed by a preset amount, so the relative system response factor summation for each car with respect to any call would change similarly. And, system operational factors such as, for example, preventing unnecessary motion of a car, saving energy by allowing cars to remain shut down unless really needed, favoring the availability of cars at a main landing such as a lobby, were all factored in, not absolutely, but based upon the reasonableness of creating delay in answering calls in exchange for a continued system operational pattern which was realistic and served other needs.
However, on the other hand, the relative system response (RSR) algorithm disclosed in the prior Bittar '381 patent used particular, preset bonuses and penalties and calculated RSR value as a function of these particular set bonuses and penalties. For each hall call that was currently registered in the group, the RSR value was computed for each car. The car having the lowest RSR value was assigned to answer the hall call, and this procedure was repeated for each hall call.
But, because the bonuses and penalties were fixed and preselected, waiting times sometimes became large, depending on the circumstances of the system. Thus, although the '381 invention was a substantial advance in the art, further substantial improvement is possible and has been achieved in the present invention.